Strain differences in the opsonisation of Staphylococcus epidermidis

Ten isolates of coagulase-negative staphylococci, collected from patients receiving treatment with continuous ambulatory peritoneal dialysis (CAPD), exhibited marked differences in the degree of opsonisation when incubated in 10% and 1% pooled human serum, 10% and 1% heat-treated serum, Hanks' Balanced Salt Solution, and timed peritoneal dialysis (PD) effluent. The addition of exogenous IgG to PD effluent results in a greater increase in opsonisation in those fluids with the weakest inherent opsonic activity, but is ineffective against the majority of isolates in the absence of heat-labile opsonic activity. The results of this in vitro study suggest that host resistance to CAPD peritonitis due to coagulase-negative staphylococci may be determined as much by the characteristics of the contaminating strain, as by the opsonising activity of PD effluent.